Glacial Evidence in the Andes Mountains, Peru
In order to answer the question, students need to identify the current ice extent, approximate the equilibrium line altitude based on dirty vs white ice (or the firn line, if visible) in summer time imagery, and document glacial landforms. They also need to recognize the correspondence between elevation and ice extent.
Key words: glaciers, glacial landforms, Google Earth
Skills and concepts that students must have mastered
How the activity is situated in the course
Content/concepts goals for this activity
- Identify the approximate equilibrium line altitude on modern glaciers from aerial imagery
- Identify glacial features, glacial landforms, and glacial deposits
- Interpret landscapes that have been glaciated
- Document ice extent from past glaciations
- Infer the nature of glacial cover in the past
Higher order thinking skills goals for this activity
Other skills goals for this activity
Description and Teaching Materials
This exercise serves as an assessment of students' knowledge in a glacial geology course. In the course, they have learned how to identify glacial landforms and deposits in Google Earth. They have also learned how to add points, lines, and areas to Google Earth imagery, and how to create topographic profiles. Further, students have completed an exercise where they conducted a comparative study of erosional landforms created by river and hillslope processes as opposed to those sculpted by alpine glaciers.
This exercise brings the students to a new landscape in the Peruvian Andes where some alpine and niche glaciers still exist. Their task is to determine glacial extent in the past, and infer the kind of glacier(s) that had existed in the area.
In order to answer the question, students need to identify the current ice extent, approximate equilibrium line altitude based on dirty vs white ice (or the firn line, if visible) in summer time imagery, and glacial landforms. They also need to recognize the correspondence between elevation and ice extent.
In Google Earth, go to latitude/longitude 9.39° S, 77.33° W and determine:
What is the current ELA for the area?
To what elevation did glaciers extend in the past? Follow signs of glaciation as far as 8.82° S, 77.04° W for evidence.
What kind of glacial setting was regionally present during full glacial conditions? Was it an ice sheet, ice cap, ice field, or alpine glacial setting? Support your conclusion with evidence (annotated screen captures, topographic profiles, and the like).
For each of the questions, make screen shots of areal imagery, topography, and topographic profiles of glacial features and landforms, and arrange them in a document. Annotate the figures. Your work will be evaluated based on clarity of imagery, correctness of identification of glacial features, and thoroughness of documentation of glacial features and ice extent.
Keep in mind that you can view topographic relief maps of the area in Google Earth, by clicking the "View in Google Maps" icon on the tool bar, and then selecting Maps–>Terrain.
Students create a document (slide show presentation or word document) with annotated figures, verbal descriptions and summary statement of glacial type in the past with a rationale based on evidence.
Teaching Notes and Tips
Student answers in the submitted document will be ranked and quantified according to a rubric with the following ranks:
- Unacceptable = 0; incorrect identification; lack of supporting evidence; incorrect inferences
- Passing, but flawed = 1; mostly correct identification; some flawed evidence and reasoning
- Adequate = 2; correct identification, sufficient evidence to support conclusions
- Excellent = 3; clear, well-annotated figures with correct identification of key glacial features; correct inference on past glacial conditions with solid supporting evidence
The following aspects of the submitted document will be evaluated and provide a summary score based on a weighted sum:
- 10%: Clarity of imagery (from screen captures in Google Earth)
- 60%: Correct identification of glacial features (ELA, end and lateral moraines, cirques, tarns, horns, aretes, etc)
- 30%: Interpretation of past glacial ice mass type (ice sheet, ice cap, ice field, alpine glaciers), with supporting evidence and line of reasoning.
The weighted sum will be re-scaled to a university curve (60-70 = D; 70-80 = C; 80-90 = B; 90-100 = A) with the following linear equation: Grade % = 60.1 + 0.4 x Rubric %.
Click here for an example implementation (Excel 2007 (.xlsx) 80kB Jun13 14) of the rubric.